This invention relates to an improved winch in general; and, in particular, to a winch arrangement that lends itself to construction in a pocket-sized version which is readily portable and suitable for lightweight winching operations.
The term "winch" as used herein, refers to a winch, hoist, block and tackle or similar mechanism having a structural housing member including a drum, pulley or sheave (hereafter called "drum") about which a flexible linear member, such as chain, cable, rope or strap, is wrapped, wound or similarly perimetrically or peripherally extended (hereafter "wrapped") for the purpose of hoisting, lowering or hauling a load. A winch of this type may, for example, take the form of a hand-cranked spool-like drum rotatably carried on a shaft or pin mounted between opposite sideplates or cheeks of the supporting structure and about which a single turn of a cable linear member is wrapped, or may take the form of a housing having multiple, motor-driven sprocketed pulleys about which multiple turns of a chain linear member are wrapped.
Of particular interest to the invention is a winch of the type wherein means is provided to fix a point of the linear member to a point on the drum for rotation therewith, so that rotation of the drum causes an increase or decrease in the number of turns of the linear member about the drum, with a resulting raising or lowering of a load fixed relative to another point of the linear member remotely-positioned away from the drum.
In a usual conventional winch arrangement of this type, one end of the linear member is secured to the winch housing or drum and the other free end of the linear member serves to mount the load, such as by means of a hook. The drum is rotated either by hand-cranking or motor driving a drum shaft. The housing is fixed to external supporting structure, which may be a frame of a building or a gantry. The weight of the load in such an arrangement is supported by the housing, as well as by the linear member.
One aspect of the present invention relates to a new load bearing arrangement for a winch, whereby the entire load may be carried by the linear member, and protection against load dropping due to slippage is provided.
Winch arrangements of the type to which the invention relates will also normally include mechanical reduction gearing of some kind or other for transferring the motion between the crank arm or motor output drive shaft and the drum at a given speed reduction ratio. A typical configuration utilizes a conventional toothed, meshing gear train positioned between the drive shaft and the drum shaft. Such gearing is normally external to the drum and therefore increases the size of the winch.
Another aspect of the present invention relates to a new reduction gearing arrangement between the drum and the crank arm or motor shaft which permits the establishment of a very compact winch configuration.
Of relevance to the mechanical gearing aspect of the invention are concentric motion transfer mechanisms, such as those described in Rabek U.S. Pat. No. 3,468,175 and Batty U.S. Pat. No. 3,507,159, which employ wave gear technology to transfer motion at a predefined speed reduction ratio between one of two cyclically undulated or cammed surfaces and an intermediate carrier of reciprocated oscillating members, such as rollers or balls. In Batty, for example (see Batty FIGS. 2 and 3), motion transfer between a cam mounted on a central drive shaft and a concentrically positioned cylindrical extension of an output shaft occurs by interaction between an elliptical external surface of the cam and an internal periodically undulated continuous cam track of a surrounding ring positioned concentrically annularly of the cylindrical extension. The extension is provided with a plurality of radially-directed apertures, evenly spaced at angularly-displaced locations thereabout and which provide guideways to confine a plurality of rollers for radially-directed, oscillatory motion respectively therein. The rollers are adapted to contact both the elliptical cam surface of the cam and the cam track of the ring. The cam track provides an annular array of evenly-spaced teeth separated by recesses. As the rollers are driven radially in and out by the inner cam surface, they are forced to move along the contour of the outer cam surface track which is fixed, thereby causing the output shaft cylindrical extension to be rotated according to a predetermined speed ratio.
In the described Batty embodiment, it is the outer ring that is held fixed while the apertured cylindrical extension which captures the rollers is permitted to move. It is recognized that if the cylindrical extension is held fixed and the outer ring permitted to move, the same motion transfer mechanism can be implemented with the rotating cam driving the outer ring. Rabek shows various embodiments (see, e.g., Rabek FIGS. 8 and 10) wherein a central cam is rotated to drive an outer ring. To Applicant's knowledge, however, such wave gear motion transfer technology has not heretofore been applied to a winch, as described herein.